This invention generally relates to the field of intravascular catheters which are advanceable over a guidewire into a desired region of a patient's vasculature, and particularly to dilatation, atherectomy catheters and the like which are advanceable into a patient's coronary arteries for therapeutic or diagnostic procedures therein.
In typical angioplasty procedures, a guiding catheter having a preshaped distal tip is percutaneously introduced by a Seldinger technique into the cardiovascular system of a patient and advanced within the system until the preshaped distal tip of the guiding catheter is disposed within the ascending aorta adjacent the ostium of the desired coronary artery. The guiding catheter is relatively stiff and when it is twisted or torqued from its proximal end, which extends outside the patient, the distal tip of the guiding catheter is guided into the desired coronary ostium. With the distal end of the guiding catheter well seated within the ostium of the desired coronary artery, a balloon dilatation catheter is introduced into and advanced through the guiding catheter and out the distal tip thereof into the patient's coronary artery until the balloon on the distal extremity of the dilatation catheter is properly positioned across the lesion to be dilated. Once properly positioned, the balloon is inflated one or more times to a predetermined size with radiopaque liquid at relatively high pressures (e.g., generally 4-12 atmospheres) to dilate the stenotic region of the diseased artery. When the dilatations have been completed, the balloon is finally deflated so that the dilatation catheter can be removed from the dilated stenosis to allow the resumption of normal blood flow through the dilated artery. The atherectomy procedures are similar except that the atheroma is severed from the arterial wall rather than the balloon expanding as in balloon angioplasty.
One frequently used type of angioplasty catheter is the over-the-wire type catheter which has an inner lumen extending within the catheter shaft which is configured to slidably receive a guidewire which facilitates advancement of the catheter over the guidewire to the desired location within the patient's coronary arteries. The guidewire receiving inner lumen may extend the entire length of the catheter as in conventional over-the-wire catheters or only in the distal portion of the catheter between a distal guidewire port and a proximal guidewire port which is spaced a short distance proximally from the distal guidewire port and a substantial distance from the proximal end of the catheter as in rapid exchange catheters.
It is not uncommon during an angioplasty procedure to exchange the dilatation catheter once the dilatation catheter has been advanced within the patient's arterial system. For example, if the physician determines that the inflated size of the balloon or the length of the balloon is inappropriate for the stenosis to be dilated, the dilatation catheter will be withdrawn and an appropriately sized dilatation catheter will be advanced into the coronary artery over the guidewire which remains in-place to dilate the stenosis. However, if the catheter is a conventional over-the-wire catheter, before the catheter is withdrawn either the guidewire in place must be replaced with an exchange wire, which is similar to the in-place guidewire except about twice as long, e.g. about 300 cm, as the normal guidewire or an extension wire about the same length as the in-place guidewire must be secured to the proximal end of the in-place guidewire to facilitate the withdrawal of the catheter without loss of the distal position of the guidewire. The reason it is important to maintain the position of the distal tip of the guidewire across the stenosis, is that if the guidewire is withdrawn, it may take the physician from about 15 minutes to about two hours or more to readvance a guidewire into the patient's coronary artery and across the stenosis to be dilated and then advance the balloon on the dilatation catheter across the stenotic region.
What has been needed and heretofore unavailable is a system for exchanging over-the-wire type and other types of intravascular catheters without the use of exchange wires or extension wires and which can hold the distal extremity of the guidewire in position within the distal end of the guiding catheter without occluding the passageway of the guiding catheter. The present invention satisfies these and other needs.